The long-term objective of our project is to identify the mechanisms which operate to regulate and maintain the increases in intestinal blood flow and oxygen uptake following a meal. Adenosine (vasodilator) and prostanoids containing both dilators (PGI2 and PGE2) and constrictors (TxA2 and PGF2a) are released postprandially from the jejunum. These chemicals exert their actions near the site of their releases, but it is not known from which tissues (mucosa and/or muscularis) and under what conditions (during nutrient absorption and/or segmental contractions) they are released. Also it is not known whether the amounts released are sufficient to contribute to postprandial regulation of local blood flow and oxygen uptake. The first aim of the project is to determine mucosal and muscle interstitial fluid adenosine concentration (ISF [Ado]) (utilizing the kinetic properties of SAH hydrolase) during nutrient absorption or segmental contractions. Aims #2 and #3 are to determine the rates of production of prostanoids (utilizing radioimmunoassay) during nutrient absorption (in vitro) and segmental contractions (in vivo), respectively. Mefenamic acid or adenosine deaminase will be utilized to determine the contribution of prostanoids or adenosine in contraction-induced hyperemia. The fourth aim is to determine whether mucosal and muscularis ISF [Ado] and prostanoid concentrations are increased sufficiently to participate in regulation of mucosal or muscularis blood flow during nutrient absorption or segmental contractions. The dietary factor plays a significant role in cardiovascular diseases, and the mechanisms involved in the regulation of postprandial intestinal blood flow and oxygen uptake differ with the type of nutrients. Therefore, the fifth aim is to determine the effects of glucose, oleic-acid, or amino-acids on intestinal production of adenosine and prostanoids. Adenosine deaminase or mefenamic acid will be utilized again to determine the contribution of adenosine and prostanoids in regulation of intestinal blood flow and oxygen uptake during absorption of each of these nutrients. The primary mucosal prostanoid, TxA2, inhibits intestinal oxygen uptake and capillary filtration coefficient during nutrient absorption. However, the exact underlying mechanism is unknown. One possible mechanism is direct inhibitory action of endogenous TxA2 on tissue oxidative metabolism. Utilizing in vitro techniques, we will determine the effects of TxA2 analogue (U-44069) and receptor antagonist (SQ-29548) on intestinal oxidative metabolism (Warburg apparatus) and glucose transport (everted intestinal sacs).